As currently designed, intelligent elevator systems incorporate built-in safety precautions to ensure that no injury will be inflicted upon users during the normal operation of the elevator. Such devices include pressure-sensitive elements to determine pressure put on a door while it is closing, optical elements to determine when someone has passed through the elevator doorway, speed tolerance governing and braking devices and the like. Recently, particularly in urban areas having many high-rise structures, people have gained access to the shaft-side roof of the elevator cab through artful and wrongful manipulation of the elevator system. One common form of unauthorized access to elevator car tops is through the placement of strings on the roller release assembly of the elevator door interlock when the elevator is servicing a floor. Once the string is attached to the interlock release assembly, the elevator doors close normally, and the elevator is sent to the next lower floor. When the elevator arrives at the next lower floor, the shoe string is pulled on the floor above allowing the exterior hoistway door to open, which in turn allows access to the top of the elevator car.
While some access to the roof of the elevator car is necessary for the performance of maintenance and repairs on the system, unauthorized entry is extremely dangerous and can easily result in severe injury or death. Thus, a need exists for a device which can detect an unauthorized intrusion and initiate a proper response upon detection. Because of the special nature of the operating environment of an elevator shaft, there exists several problems not readily ascertainable or solvable by the use of a wide variety of detection techniques. For example, the constant vibration of the elevator cab within the shaft would cause severe problems for a reflective optical system because of the misalignment created between source and reflector by the vibrations. Similarly, false detections can easily be made because of the effect on a beam caused by the high volume of dust and particles present in the shaft space. Pressure-sensitive detectors are also not a viable alternative because of the extreme pressure changes which occur in the shaft as the elevator cab moves within it. Further, these systems do not lend themselves to servicing nor do they permit the elevator system to return to normal operation when an intruding object is removed. A need exists, therefore, for a reliable detection device which can be easily installed and maintained, and which can accurately detect the entry onto an elevator cab roof without giving false warnings.
It is an object of the present invention to provide a reliable intrusion detection system for use on the shaft-side roof of an elevator cab.
It is a further object of the present invention to provide an intrusion detection system for use on the shaft-side roof of an elevator cab which can detect an unauthorized entry onto the roof and produce an appropriate response.
It is a further object of the present invention to provide an intrusion detection system for use on the shaft-side roof of an elevator cab which will not produce false indications of an intrusion based on the operating environment of the elevator shaft and which will allow the elevator system to be easily serviced and will allow it to return to normal operation if an object intrudes upon the cab roof and is immediately thereafter removed from the cab roof.
It is a still further object of this invention to employ a proximity detection system in conjunction with a switching network to detect unauthorized entry onto a elevator cab roof on the shaft-side of the cab.